Visualizing the structural and chemical heterogeneity of fruit and vegetables using advanced imaging techniques: fundamentals, instrumental aspects, applications and future perspectives.

Fruit and vegetables (F&V) are vastly complicated products with highly diverse chemical and structural characteristics. Advanced imaging techniques either combine imaging with spectral information or can provide excellent tissue penetration, and enable the possibility to target, visualize and even qualify the chemical and physical (structural) heterogeneity within F&V. In this review, visible and/or near infrared hyperspectral imaging, Fourier transform infrared microspectroscopic imaging, Raman imaging, X-ray and magnetic resonance imaging to reveal chemical and structural information in a spatial context of F&V at the macro- (entire products), meso- (tissues), and micro- (individual cells) scales are comprehensively summarized. In addition, their basic concepts and operational procedures, particularly sample preparation and instrumental parameter adjustments, are addressed. Finally, future challenges and perspectives of these techniques are put forward. These imaging techniques are powerful tools to assess the biochemical and structural heterogeneity of F&V. Cost reduction, sensor fusion and data sharing platforms are future trends. More emphasis on aspects of knowledge and extension at the level of academia and research, especially on how to select techniques, choose operational parameters and prepare samples, are important to overcome barriers for the wider adoption of these techniques to improve the evaluation of F&V quality.

Hyperspectral imaging reveals chemical heterogeneity of fruit and vegetables.Imaging techniques provide spatial insights in fruit and vegetables at multiple scales.Future trends are cost reduction, sensor fusion and data sharing.Instrumental adjustment and sample preparation should receive more attention.

MicroRNA expression signature in the striated and smooth adductor muscles of Yesso scallop Patinopecten yessoensis.

Increasing evidences point to the potential role of microRNAs (miRNAs) in muscle growth and development in animals. However, knowledge on the identity of miRNAs and their targets in molluscs remains largely unknown. Scallops have one large adductor muscle, composed of fast (striated) and slow (smooth) muscle types, which display great differences in muscle fibers, meat quality, cell types and molecular components. In the present study, we performed a comprehensive investigation of miRNA transcriptomes in fast and slow adductor muscles of Yesso scallop Patinopecten yessoensis. As a result, 47 differentially expressed miRNAs representing ten miRNA families were identified between the striated and smooth adductor muscles. The KEGG enrichment analysis of their target genes were mainly associated with amino acid metabolism, energy metabolism and glycan biosynthesis. The target genes of miR-133 and miR-71 were validated by the dual-luciferase reporter assays and miRNA antagomir treatment in vivo. The identification and functional validation of these different miRNAs in scallops will greatly help our understanding of miRNA regulatory mechanism that achieves the unique muscle phenotypes in scallops. The present findings provide the direct evidences for muscle-specific miRNAs involved in muscle growth and differentiation in molluscs.

Exploration of molecular interaction between different plant proteins and 2-pentylfuran: based on multiple spectroscopy and molecular docking.

BACKGROUND: Soy protein, peanut protein and wheat protein are commonly applied in plant-based products, but specific off-odor makes it difficult for consumers to accept, with 2-pentylfuran being one of the most representative flavors. In this study, 2-pentylfuran was employed as an example to explore the behavior and mechanism of the three proteins in absorbing off-odors. RESULTS: Gas chromatographic-mass spectrometric analysis indicated that different plant proteins were able to adsorb 2-pentylfuran. Circular dichroism proved 2-pentylfuran could drive the α-helix to ß-sheet transition of soy protein, which was not obvious in peanut protein or wheat protein. Ultraviolet spectroscopy tentatively determined that 2-pentylfuran caused changes in the tyrosine and tryptophan microenvironments of different plant proteins, which were further evidenced by synchronous fluorescence at fixed wavelength intervals of 15 nm and 60 nm. Static quenching of protein intrinsic fluorescence indicated that they formed a stable complex with 2-pentylfuran, except for wheat protein (dynamic quenching). CONCLUSION: The various conformations of the three proteins are the main reason for the difference in flavor retention of protein. Soy protein, peanut protein and wheat protein adsorbing 2-pentylfuran relies on non-covalent forces, especially hydrophobic interactions, maintained between the protein and 2-pentylfuran. © 2023 Society of Chemical Industry.

Revealing the reasons for the pasting property changes of rice during aging from the perspective of starch granule disaggregation.

BACKGROUND: The pasting properties of rice change markedly after aging, although the mechanism for this still remains unknown. Aged and fresh rice grains were ground and the flours were fractionated by particle size, and then the pasting properties, particle size distribution and microscopic morphology of the heated flour fractions were evaluated. RESULTS: Compared to the corresponding fresh flour fractions with the same particle size, a lower peak viscosity for those aged flour fractions from 80 µm to 450 µm and a higher peak viscosity for those aged flour fractions from 20 µm to 60 µm were observed. The amounts of smaller particles disaggregated from the aged flour fractions were significantly less and the separated entities were always larger than the corresponding fresh rice fractions. CONCLUSION: Disaggregation difficulty of starch granules was the reason for the changes in the pasting properties of rice after aging. This finding is helpful for understanding rice aging mechanisms and regulating eating quality of rice flour as an ingredient. © 2022 Society of Chemical Industry.

Growth Prediction of the Total Bacterial Count in Freshly Squeezed Strawberry Juice during Cold Storage Using Electronic Nose and Electronic Tongue.

The growth models of total bacterial count in freshly squeezed strawberry juice were established by gas and taste sensors in this paper. By selecting the optimal sensors and fusing the response values, the Modified Gompertz, Logistic, Huang and Baranyi models were used to predict and simulate the growth of bacteria. The results showed that the R2 values for fitting the growth model of total bacterial count of the sensor S7 (an electronic nose sensor), of sweetness and of the principal components scores were 0.890-0.944, 0.861-0.885 and 0.954-0.964, respectively. The correlation coefficients, or R-values, between models fitted by the response values and total bacterial count ranged from 0.815 to 0.999. A single system of electronic nose (E-nose) or electronic tongue (E-tongue) sensors could be used to predict the total bacterial count in freshly squeezed strawberry juice during cold storage, while the higher rate was gained by the combination of these two systems. The fusion of E-nose and E-tongue had the best fitting-precision in predicting the total bacterial count in freshly squeezed strawberry juice during cold storage. This study proved that it was feasible to predict the growth of bacteria in freshly squeezed strawberry juice using E-nose and E-tongue sensors.

Rapid Non-Destructive Quantification of Eugenol in Curdlan Biofilms by Electronic Nose Combined with Gas Chromatography-Mass Spectrometry.

Eugenol is hepatotoxic and potentially hazardous to human health. This paper reports on a rapid non-destructive quantitative method for the determination of eugenol concentration in curdlan (CD) biofilms by electronic nose (E-nose) combined with gas chromatography-mass spectrometry (GC-MS). Different concentrations of eugenol were added to the film-forming solution to form a series of biofilms by casting method, and the actual eugenol concentration in the biofilm was determined. Analysis of the odor collected on the biofilms was carried out by GC-MS and an E-nose. The E-nose data was subjected to principal component analysis (PCA) and linear discriminant analysis (LDA) in order to establish a discriminant model for determining eugenol concentrations in the biofilms. Further analyses involving the application of all sensors and featured sensors, the prediction model-based partial least squares (PLS) and support vector machines (SVM) were carried out to determine eugenol concentration in the CD biofilms. The results showed that the optimal prediction model for eugenol concentration was obtained by PLS at R2p of 0.952 using 10 sensors. The study described a rapid, non-destructive detection and quantitative method for determining eugenol concentration in bio-based packaging materials.

Grading and Sorting of Grape Berries Using Visible-Near Infrared Spectroscopy on the Basis of Multiple Inner Quality Parameters.

The potential of visible-near infrared (vis/NIR) spectroscopy (400 nm to 1100 nm) for classification of grape berries on the basis of multi inner quality parameters was investigated. Stored Vitis vinifera L. cv. Manicure Finger and Vitis vinifera L. cv. Ugni Blanc grape berries were separated into three classes based on the distribution of total soluble solid content (SSC) and total phenolic compounds (TP). Partial least squares regression (PLS) was applied to predict the quality parameters, including color space CIELAB, SSC, and TP. The prediction results showed that the vis/NIR spectrum correlated with the SSC and TP present in the intact grape berries with determination coefficient of prediction (RP2) in the range of 0.735 to 0.823. Next, the vis/NIR spectrum was used to distinguish between berries with different SSC and TP concentrations using partial least squares discrimination analysis (PLS-DA) with >77% accuracy. This study provides a method to identify stored grape quality classes based on the spectroscopy and distributions of multiple inner quality parameters.

A splicing-independent function of SF2/ASF in microRNA processing.

Both splicing factors and microRNAs are important regulatory molecules that play key roles in posttranscriptional gene regulation. By miRNA deep sequencing, we identified 40 miRNAs that are differentially expressed upon ectopic overexpression of the splicing factor SF2/ASF. Here we show that SF2/ASF and one of its upregulated microRNAs (miR-7) can form a negative feedback loop: SF2/ASF promotes miR-7 maturation, and mature miR-7 in turn targets the 3'UTR of SF2/ASF to repress its translation. Enhanced microRNA expression is mediated by direct interaction between SF2/ASF and the primary miR-7 transcript to facilitate Drosha cleavage and is independent of SF2/ASF's function in splicing. Other miRNAs, including miR-221 and miR-222, may also be regulated by SF2/ASF through a similar mechanism. These results underscore a function of SF2/ASF in pri-miRNA processing and highlight the potential coordination between splicing control and miRNA-mediated gene repression in gene regulatory networks.

Classification and Discrimination of Different Fungal Diseases of Three Infection Levels on Peaches Using Hyperspectral Reflectance Imaging Analysis.

Peaches are susceptible to infection from several postharvest diseases. In order to control disease and avoid potential health risks, it is important to identify suitable treatments for each disease type. In this study, the spectral and imaging information from hyperspectral reflectance (400~1000 nm) was used to evaluate and classify three kinds of common peach disease. To reduce the large dimensionality of the hyperspectral imaging, principal component analysis (PCA) was applied to analyse each wavelength image as a whole, and the first principal component was selected to extract the imaging features. A total of 54 parameters were extracted as imaging features for one sample. Three decayed stages (slight, moderate and severe decayed peaches) were considered for classification by deep belief network (DBN) and partial least squares discriminant analysis (PLSDA) in this study. The results showed that the DBN model has better classification results than the classification accuracy of the PLSDA model. The DBN model based on integrated information (494 features) showed the highest classification results for the three diseases, with accuracies of 82.5%, 92.5%, and 100% for slightly-decayed, moderately-decayed and severely-decayed samples, respectively. The successive projections algorithm (SPA) was used to select the optimal features from the integrated information; then, six optimal features were selected from a total of 494 features to establish the simple model. The SPA-PLSDA model showed better results which were more feasible for industrial application. The results showed that the hyperspectral reflectance imaging technique is feasible for detecting different kinds of diseased peaches, especially at the moderately- and severely-decayed levels.

Hot air treatment reduces postharvest decay and delays softening of cherry tomato by regulating gene expression and activities of cell wall-degrading enzymes.

BACKGROUND: Fruit softening facilitates pathogen infection and postharvest decay, leading to the reduction of shelf-life. Hot air (HA) treatment at 38 °C for 12 h is effective in reducing postharvest disease and chilling injury of tomato fruit. To explore the effect and mechanism of HA treatment on reducing postharvest decay and softening of cherry tomato, fruit at the mature green stage were treated with HA and then stored at 20 °C for 15 days. Changes in natural decay incidence, firmness, cell wall compositions, activities and gene expression of cell wall-degrading enzymes of cherry tomatoes were assessed. RESULTS: HA treatment reduced natural decay incidence, postponed the firmness decline, inhibited the respiration rate and ethylene production, and retarded pectin solubilisation and cellulose degradation of cherry tomatoes. Enzymatic activities and gene expression of pectin methylesterase, polygalacturonase, cellulase and ß-galactosidase were inhibited by HA treatment. In addition, the gene expression of LeEXP1 was reduced, while LeEXT was up-regulated after HA treatment. CONCLUSIONS: Our findings suggested that HA treatment could inhibit cell wall degradation and postpone softening of cherry tomatoes by regulating gene expression and activities of cell wall-degrading enzymes, resulting in the reduction of postharvest decay. © 2017 Society of Chemical Industry.

Rapid detection of adulterated peony seed oil by electronic nose.

Peony seed oil has recently been introduced as a high-quality food oil. Because the high price of peony seed oil may tempt unscrupulous merchants to dilute it with cheaper substitutes, a rapid detection method for likely adulterants is required. In this study, the fatty acid composition of peony seed oil and four less expensive edible oils (soybean oil, corn oil, sunflower oil, and rapeseed oil) were measured by gas chromatography mass spectrometry. Peony oil adulterated by other edible oils was assessed using iodine values to estimate the extent of adulteration. Adulteration was also measured using an electronic nose (E-nose) combined with principal component analysis (PCA) or linear discriminant analysis (LDA). Results indicated that peony seed oil was highly enriched in α-linolenic acid. Although the iodine value can be used to detect some adulterants by measuring unsaturation, it was not able to detect all four potential adulterants. In contrast, the E-nose can rapidly identify adulterated peony seed oil by sampling vapor. Data analyses using PCA and LDA show that LDA more effectively clusters the data, discriminates between pure and adulterated oil, and can detect adulteration at the 10% level. E-nose combined with LDA suitable for detection of peony seed oil adulteration.

Comparison of Benchtop Fourier-Transform (FT) and Portable Grating Scanning Spectrometers for Determination of Total Soluble Solid Contents in Single Grape Berry (Vitis vinifera L.) and Calibration Transfer.

Near-infrared (NIR) spectroscopy was applied for the determination of total soluble solid contents (SSC) of single Ruby Seedless grape berries using both benchtop Fourier transform (VECTOR 22/N) and portable grating scanning (SupNIR-1500) spectrometers in this study. The results showed that the best SSC prediction was obtained by VECTOR 22/N in the range of 12,000 to 4000 cm-1 (833-2500 nm) for Ruby Seedless with determination coefficient of prediction (Rp²) of 0.918, root mean squares error of prediction (RMSEP) of 0.758% based on least squares support vector machine (LS-SVM). Calibration transfer was conducted on the same spectral range of two instruments (1000-1800 nm) based on the LS-SVM model. By conducting Kennard-Stone (KS) to divide sample sets, selecting the optimal number of standardization samples and applying Passing-Bablok regression to choose the optimal instrument as the master instrument, a modified calibration transfer method between two spectrometers was developed. When 45 samples were selected for the standardization set, the linear interpolation-piecewise direct standardization (linear interpolation-PDS) performed well for calibration transfer with Rp² of 0.857 and RMSEP of 1.099% in the spectral region of 1000-1800 nm. And it was proved that re-calculating the standardization samples into master model could improve the performance of calibration transfer in this study. This work indicated that NIR could be used as a rapid and non-destructive method for SSC prediction, and provided a feasibility to solve the transfer difficulty between totally different NIR spectrometers.

Isolation of broad-specificity domain antibody from phage library for development of pyrethroid immunoassay.

An antibody to phenoxybenzoic acid (PBA), the conserved chemical region of pyrethroids, was developed using a domain antibody (DAB) library to enable pyrethroid detection in agricultural products. The DAB library, constructed without animal immunization and based on a human VH framework, displayed repertoires on filamentous bacteriophage. After four rounds of panning, we obtained five domain antibodies that are capable of binding to PBA. Antibody A3 has strong identification capability to cypermethrin, ß-cypermethrin, and fenvalerate. The antibody A3 was used to develop an enzyme-linked immunosorbent assay (ELISA). The IC50 values were 2.586, 1.814, and 2.251 µg/ml for cypermethrin, ß-cypermethrin, and fenvalerate, respectively. The assay shows weak competition with flucythrinate but shows no competition with fenpropathrin, deltamethrin, and permethrin. The developed ELISA process was successfully applied to fortified Chinese cabbage samples, with the recoveries of cypermethrin, ß-cypermethrin, and fenvalerate ranging from 84.4 to 112.3%. We developed an immunoassay to detect pyrethroids depending on the domain antibody library, which overcomes the limitation of requiring protein antigen to immunize animals raising antibody.

[Effect of Telbivudine Tablet Combined Jianpi Bushen Recipe on HBV Specific Cytotoxic T Lymphocyte and HBeAg Seroconversion in Patients with HBeAg Positive Chronic Hepatitis B].

OBJECTIVE: To explore the effect of Telbivudine (LDT) Tablet combined with Jianpi Bushen Recipe (JBR) on serum hepatitis B virus (HBV) specific cytotoxic T lymphocyte (CTL) and HBeAg seroconversion in chronic hepatitis B (CHB) patients. METHODS: Totally 90 HBeAg-positive and human leukocyte antigen (HLA)-A2 positive CHB patients were randomly assigned to the treatment group and the control group, 45 cases in each group. Patients in the treatment group took LDT Tablet (600 mg, once per day) combined with JBR granule (twice per day), while those in the control group took LDT Tablet alone. The therapeutic course for all was one year. HBV DNA negative conversion rate, HBeAg seroconversion rate, and level of HBV specific CTL were compared after 1 year treatment; liver function, drug resistance mutations, and adverse reactions were also compared between the two groups. RESULTS: After 1 year treatment, HBV DNA negative conversion rate and HBeAg seroconversion rate were 88.89% (40/45) and 40.00% (18/45) in the treatment group, higher than those of the control group [68.89% (31/45) and 20.00% (9/45)], with statistical difference (P < 0.05). Level of HBV specific CTL in the treatment group was 0.78% +/- 0.09% after treatment, higher than that of the control group after 1 year treatment (0.54% +/- 0.11%) and that before treatment (0.36% +/- 0.07%), with statistical difference (P < 0.01). Level of HBV specific CTL in 27 patients with HBeAg seroconversion was 0.81% 0.10%, higher than that of 63 patients without HBeAg seroconversion (0.60% +/- 0.09%), with statistical difference (P < 0.01). ALT returned to normal in 44 cases of the treatment group (97.78%), while it was 42 cases (93.33%) of the control group, with no statistical difference between the two groups (P > 0.05). Total bilirubin (TBil) in the two groups all turned to normal. rtM204I variation occurred in 1 case (2.22%) of the treatment group and 2 cases (4.44%) in the control group. No obvious adverse reaction occurred in the two groups. CONCLUSION: LDT Tablet combined with JBR could elevate levels of HBV specific CTL and HBeAg seroconversion in CHB patients.

[Effect of compound qizhu granule on cellular immunity of chronic hepatitis B patients].

OBJECTIVE: To explore the effect of compound qizhu granule (CQG) on cellular immunity of chronic hepatitis B (CHB) patients. METHODS: Totally 103 CHB patients treated with lamivudin (LAM) for 6 months, who had partial virological response (HBeAg positive) were randomly assigned to two groups, 50 in the treatment group and 53 in the control group. All patients took LAM 100 mg (once a day) plus ADV 10 mg (once a day). Patients in the treatment group additionally took CQG, one dose per day. After one-year treatment hepatitis B virus (HBV) DNA negative rates, HBeAg seroconversion, levels of HBV specific cytotoxic T lymphocyte (CTL), non-specific CTL and natural killing (NK) cells were compared between the two groups. RESULTS: After 1-year treatment, HBV DNA negative rate of the treatment group was 88: 0% in 44 cases, slightly higher than that of the control group (41 cases, 77.4%), but with no statistical difference (P >0.05). HBeAg seroconversion of the treatment group was 32.0% in 16 cases, higher than that of the control group (8 cases, 15.1%), with statistical difference (P <0.05). Levels of HBV specific CTL (0.79%±0. 07%), non-specific CTL (19.4%±1.8%) and NK cells (14. 1%± 1.5%) of the treatment group were higher than those of the control group (0.58% ± 0.08%, 17.5% ± 1.7%, and 11.1%±1.5%, respectively; allP <0.01). CONCLUSION: Treating CHB patients with partial virological response by ADV plus CQG could improve specific and non-specific cellular immunity, thereby elevating HBeAg seroconversion rate.

Study on color and flavor changes of 4D printed white mushroom gel with microcapsules containing gelatin / ß-cyclodextrin induced by microwave heating.

The feasibility of microwave heating to induce color/flavor changes of 4D printed white mushroom gel containing curcumin or γ-dodecalactone (γ-DDL) microcapsules was studied. Using gelatin/ ß-cyclodextrin as wall material and soy protein isolate as emulsifier, microcapsules containing curcumin or γ-DDL were prepared by spray drying method. The microcapsules containing curcumin were mixed into white mushroom powder at different mass ratios (0, 0.1, 1, 3, 5 %, w/w) as printing ink. With the increase of microcapsule content, the viscosity, storage modulus and loss modulus of printing ink increased, but the water distribution and recovery performance did not change significantly. With the extension of heating time, the brightness value (L*) and the redness value (a*) of the printed sample increased, and the yellowness value (b*) decreased. After adding 3 % (w/w) microcapsules containing γ-DDL, the content change of the target flavor substance in the printed sample during microwave treatment was determined based on Gaschromatography-mass spectrometry (GC-MS). The results showed that microwave treatment could promote the release of flavor substances, and the content was 272.37 µg/kg when heated for 3 min. This study provides a new idea for the development of 4D printed food with special color and target flavor based on microcapsule technology.

Investigation of 3D printing product of powder-based white mushroom incorporated with soybean protein isolate as dysphagia diet.

The elderly people are prone to dysphagia due to weakened muscle strength. 3D food printing could modify the nutritional ratio and shape design to produce personalized nutritious food suitable for patients with dysphagia. White mushroom (Agaricus bisporus) is rich in a variety of active ingredients such as polysaccharides and polyphenols which are beneficial to human body, but its unique texture is not suitable for patients with dysphagia to chew. This study investigated the impact of different concentrations of soybean protein isolate (SPI, 3%, 5%, 7%, w/w) on 3D food printing of white mushroom powder and carried out the hierarchical representation of dysphagia diet within the framework of International Dysphagia Diet Standardization Initiative (IDDSI). The results illustrated that SPI addition to white mushroom gel reduced water mobility and promoted hydrogen bond formation, which significantly improved the mechanical strength and cohesiveness of printing inks, including yield stress, viscosity and hardness. IDDSI tests showed that the SPI addition of 3% and 5% helped the printing ink pass the spoon tilt test and the fork drip test, which could be classified as level 5 minced and moist food under the consideration of the fork pressure test. The 3D printing results indicated that the 7% SPI addition made the yield stress too high and was not easy for extrusion, resulting in the appearance defects of the printed sample. The addition of 3% SPI could make the printed sample have smooth surface and excellent self-supporting capacity. This work provides insights of white mushroom 3D printing technology as a more visually appealing dysphagia diet.

Oil addition increases the heat resistance of Clostridium sporogenes spores in braised sauce beef: Perspectives from spore surface characteristics and microstructure.

During thermal processing of braised sauce beef, the lipid content of circularly used sauce increased accordingly because of lipid migration from beef to sauce, which may impact the bacterial heat resistance in the products. This study aims to characterize the heat resistance of Clostridium sporogenes spores in braised sauce beef, and investigate the effects of oil on the spore surface characteristics and microstructure. The results indicated that the heat resistance of C. sporogenes spores in beef was significantly higher than that in sauce. Oil addition remarkably enhanced the spore heat resistance in sauce, with D95°C value three times more than that without oil added, and even higher than that in beef. The results of spore surface characteristics indicated that oil addition led to an increase of hydrophobicity and a decrease of zeta potential, which ultimately increased spore heat resistance. Microstructure analysis indicated that exosporium maintenance and cortex expansion induced by oil addition might contribute to the increase of spore heat resistance. This study has sufficiently verified the importance of oil content on the heat resistance of C. sporogenes spores, which should be taken into consideration when developing thermal processes for controlling the spores in food matrices.

Use of optical absorption and scattering properties to monitor the change of chemical characteristics, particle structure and viscoelasticity during apple puree processing.

This work explored the optical absorption (µa) and reduced scattering (µs') properties at 400-1050 nm (Vis-NIR) and 900-1650 nm (SWIR) of apple puree at different heating times to evaluate their changes in composition and structure. The optical absorption and scattering coefficients of µa and µs' decreased with increasing heating time. The specific µs' coefficients at 432 nm, 455 nm, 1183 nm and 1304 nm were related to particle structural changes. The partial least squares regression (PLSR) models based on µs' coefficients in the combined Vis-NIR and SWIR regions provided satisfactory estimations of puree particle area (Rp2 = 0.90) and particle perimeter (Rp2 = 0.85), whereas the µs' coefficients in the Vis-NIR region predicted puree viscosity (Rp2 = 0.83), elasticity modulus (Rp2 = 0.81) and viscous modulus (Rp2 = 0.78). Consequently, optical properties can be a potential tool to determine structural and rheological changes of apple puree.

Effect of magnetic field pretreatment on germination characteristics, phenolic biosynthesis, and antioxidant capacity of quinoa.

The development of quinoa-based functional foods with cost-effective methods has gained considerable attention. In this study, the effects of magnetic field pretreatment on the germination characteristics, phenolic synthesis, and antioxidant system of quinoa (Chenopodium quinoa Willd.) were investigated. The results showed that the parameters of magnetic field pretreatment had different effects on the germination properties of five quinoa varieties, in which Sanjiang-1 (SJ-1) was more sensitive to magnetic field pretreatment. The content of total phenolics and phenolic acids in 24-h germinated seeds increased by 20.48% and 26.54%, respectively, under the pretreatment of 10 mT magnetic fields for 10 min compared with the control. This was closely related to the activation of the phenylpropanoid pathway by increasing enzyme activities and gene expression. In addition, magnetic field improved 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radicals scavenging capacities and increased peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione peroxidase (GSH-Px) activities. This study suggests that magnetic field pretreatment enhanced gene expression of phenylalanine ammonia lyase (PAL), 4-coumarate-CoA ligase (4CL), chalcone synthase (CHS) and chalcone isomerase (CHI), increased antioxidant enzyme activity and phenolics content. Thereby lead to an increase in the antioxidative capacity of quinoa.